Classics, Singles and Two Strokes
The following installation guide is a general guide for classic motorcycles, single cylinder motorcycles and two stroke motorcycles.
Some single cylinder motorcycles have twin carbs. This includes pre fuel injected BMW F650’s, and some Aprilia Pegasos. Single cylinders with twin carbs have a vacuum point to balance the carbs. Picture of bung is shown left, and balance pipe shown below left on a 4 carb model. Twin carbs can have the same.
If this is the case, tee into the pipe, or replace the bung with a damper elbow, see our Installation page.
If your single cylinder motorcycle has only one carb, then the installation for it, and many classic bikes and two strokes is as follows:-
Example Installation
The picture on the left, and below left and right, show this procedure on the BMW F650 Fi 2000 .
Other bikes are very similar, and following this basic procedure will allow you to fit your vacuum connection easily.
A single carburetor with a vacuum connector ( Yamaha XT500 1980 model)
Drilling and tapping a rubber inlet manifold
For bikes with single carburetors, it is necessary to drill the inlet tract. This can be quite straightforward if the rubber manifold between the cylinder head and the carburetor is long enough to accept the m5 or m6 spigot supplied in the kit.
Remove the rubber inlet manifold. Drill a 4mm hole in the inlet manifold, being careful to remove any swarf created. Fit the M5 spigot from the Scottoiler kit, using a silicon type sealer to ensure an airtight seal, and washers supplied in the kit, as shown left.
Re-install the rubber inlet manifold.
Drilling and tapping a carburetor / throttle body
On some models there is no space for a spigot in the rubber manifold. If this is the case the carburetor (or throttle body on fuel injected models) must be removed, drilled and have a thread cut to accept the M5 (or M6) brass spigots supplied with the vSystem. This must be forward of the slide or butterfly.
It is best to use the M5 spigot (the M6 spigot can be used should there be any problems with the M5). Always cover the open inlet on the cylinder head with a clean cloth to avoid the risk of contamination. Before drilling the hole make sure it is in the correct position, and the spigot and vacuum damper (or vacuum tubing) do not touch the throttle cables or mechanism when the parts are re-assembled on the engine.
Drill a 4.2mm hole and cut an M5 thread for M5 spigot (5.2mm hole and M6 thread for M6 spigot). Ensure there are no metal particles on the carburetor or throttle body before re-assembly.
Insert the spigot, using a washer and thread lock or silicon in the threads to ensure an airtight seal. Carefully install the throttle body or carburetor onto the engine and push the vacuum damper onto the spigot. Route the vacuum tubing neatly to your chosen RMV position.
